Particle separator for engine air inlets



July 21, 1970 H. D. CONNORS ETAL PARTICLE SEPARATOR FOR ENGINE AIRINLETS 2 sheets-sheet 1 Filed April 28, 1969 1N VENTORS.

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United States Patent 3,521,431 PARTICLE SEPARATOR FOR ENGINE AIR INLETSHarold D. Connors and Fred D. Buckley, Milford, Conn.,

assignors to Avco Corporation, Stratford, Conn., a corporation ofDelaware Filed Apr. 28, 1969, Ser. No. 819,892 Int. Cl. B01d 45/12 US.Cl. 55-306 ABSTRACT OF THE DISCLOSURE An apparatus to separate andremove foreign particles from the air supply to gas turbine engines isdisclosed. The contaminated air is drawn through first and secondcentrifugal separating stations during which centrifugal forces act onthe particles. The particle contaminants and carrier air from the secondseparating station are transmitted to a tertiary separating station tobe again cleaned. Cleaned air from each of the separating stationsreturns to the engine inlet. Particle contaminants from the tertiarystation are removed from the system and may be ejected from theseparator.

BACKGROUND OF THE INVENTION This invention relates to a particleseparator for use adjacent the air inlet of a gas turbine engine toremove foreign matter such as sand and dust from the air stream.

Air craft turbine engines are particularly susceptible to damage fromforeign objects introduced into the air intake stream of the gas turbineengines. Stones, gravel and other foreign matter drawn into the airstream often rupture, distort, and damage blades and other componentparts of the engine. These particles, which individually have littleeffect on the engine, can cause very substantial damage when introducedinto the engine in large quantities. For example, it has been found thatthe engine of a helicopter operating at low altitude in a desertenvironment can lose performance due to erosion of engine blading byhigh velocity sand particles. In addition, the desired balancedcondition of the compressor is often disrupted and the useful life ofthe engine shortened, if it is not completely destroyed.

The importance of removing small foreign particles, such as sand anddust, has long been recognized. Many mechanisms for accomplishing thispurpose are known in the art. One example is the separator shown in US.Pat. 3,371,471 to H. D. Connors. However, the present invention providescertain improvements recognized as important. Some improvements andadvantages of the present invention are the self-cleaning capability,minimal maintenance requirements, compact, lightweight, accessibility,small volume, low pressure loss, small amount of power required to ejectcontaminant and effectiveness over a broad range of particle size fromfull design flow to V2 flow.

Accordingly, it is an object of this invention to provide a lightweightand compact separator for effectively removing particles from the airstream supplied to a gas turbine engine.

3 Claims I PatentedJuly 21, 1970 "ice A further object of this inventionis to provide a sepa rator with the above-mentioned advantages.

SUMMARY OF THE INVENTION This invention provides an improved particleseparator for removing particles from the stream of air supplied to theinlet of a gas turbine engine. The particle separator utilizescentrifugal forces acting on the particles in the first two separatingstations to separate the particles from the stream of air. Air cleanedfrom the second separating station is in communication with the main airstream and is returned therein upstream of the engine air inlet. Atertiary air cleaning station is used for final cleaning and removal ofthe particle contaminant.

Other details, uses, and advantages of this invention will becomeapparent as the following description of the exemplary embodimentthereof presented in the accompanying drawings proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings show presentexemplary embodiments of this invention in which:

FIG. 1 is alongitudinal cross-section taken substantially on a sectionthrough the separator assembly in a vertical plane and showing'thelongitudinal axis of rotation of the power shaft of the engine extendingforward of the annular air inlet to the engine;

FIG. 2 is an enlarged diagrammatic representation showing the first andsecond separating stations; and

FIG. 3 is a cross-sectional view, not to scale, taken on the line 3-3 ofFIG. 1.

DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT Reference is now made to FIG.1 which illustrates one exemplary embodiment of the improved particleseparator of this invention, which is designated generally by thereference numeral 10. The separator assembly 10 is designed for mountingon the front of a gas turbine 12, having an annular air inlet 14 and aforwardly extending gear case 16 and propeller or power shaft 18. Theforwardly extending power shaft 18 may not be present in the purelyjet-type engine, but would be present in a socalled turbos'haft-type gasturbine engine of the present exemplary embodiment.

The specific structure illustrated in FIG. 1 is a crosssection of anannular separator assembly 10 with the longitudinal axis of the shaft 18or the axis of the engine as a center. The first centrifugal separatingstation, shown generally at 11, is of a radial inflow bellmouth formhaving an annular air inlet 20 extending from an outward region in agenerally radial inward direction with an outer curved wall 22 and aninner curved wall 24. The annular member 22 terminates closely adjacentto an annular curved deflector element or wall 26. The inner curved wall22 is of such configuration, bending in a curved direction toward theair inlet 14 so that air entering in a radial direction into the inlet20 will be caused to move in a curved path and any particles heavierthan air will be thrown by centrifugal force and flow direction toimpinge upon the wall .22 during the curved air movement and particlesso impinging will be deflected and intercepted by wall 26. Side splittervanes 23 may be mounted in inlet 20 to prevent a tangential particlepath 3 and to guide the particles to improve the separatoreffectiveness.

The deflector wall 26 forms the outer wall of a second centrifugalseparating station designated generally as 28. Passages 27 and 29 formthe outlets for the second separating station 28. Passage 27 is an innerannulus and is in communication with a teritary or third separatingstation 34. Passage 29 is a clean air passage for removing cleaned air,sometimes called the secondary air stream, from the second separatingstation. The wall 26 is formed so that an extension of the wall providesa secondary air passage 31 which is in communication with passage 29.Thus, clean air from the second separating station can be reinsertedinto the main air stream upstream of air inlet 14 and downstream of theinlet 20 of the first separating station.

As best seen in the diagrammatic representation of FIG. 2, air havingparticles shown generally as 30 entrained therein is drawn into thefirst separating station inlet 20. This air, generally represented bydashed arrows, is drawn through a turn during which time, because of thecentrifugal forces acting on the particles, the particles 30 are castonto the outer flow wall 22 while the clean air, or the main air streamis drawn into the engine inlet 14. It has been found that approximately90% of the air is drawn into the engine inlet passage while of the airenters the second separating station as carrier or transport air. Theparticles 30, carried by the small amount of transport air, are caughtby the deflector wall 26 and turned into the second separating station28. The particles are then centrifugally thrown toward the curvedannulus 32, forming a part of the second separating station 28 anddeflector element 26. In this second centrifugal separating station,approximately 90% of the carrier air, which is 10% of the main airstream, will be drawn off through passage 29 as clean air and theremaining 10% of the carrier air or equivalent to approximately 1% ofthe main air stream becomes the carrier air for particles 30 to betransmitted through passage 27 to the third separating station. Theclean air from the second separating station or secondary air stream isinserted into the main air stream through passage 31.

Particles from separating station 28 are transmitted through passage 27and inlet 33 to a third separating station which is best seen in FIGS. 1and 3. The third separating station, shown generally as 34, comprises aplurality of cyclonic or vortex type separator tubes 36 mounted in achamber 35. The operation of the cyclonic separators 36 are such that,as an example, the particleladen air is admitted past inclined guideblades or through a tangential inlet into a chamber, called a cyclonechamber, whereby the air is set spinning therein and by the centrifugalforce thus engendered, concentrates the particles toward the peripheryof the cyclone chamber. The concentrated particles are discharged at theperiphery of each cyclone chamber to a collection area 38 and theparticle-free air passes on straight through the cyclone separator to aclean air chamber 39 and through exit 40 into the secondary air streamwhich is in communication with the secondary air passage 31. Hence, boththe secondary and tertiary cleaned air reenters the main air stream frompassage 31.

The concentrated particles 30 are accumulated in area 38 and ejectedoverboard through an ejector 42. The ejection may be a continuousoperation or intermittent as the design dictates. In the illustrativeembodiment shown, air from the engine bleed is connected at 44, toprovide the motive power for ejection of the contaminant overboard. Itis noted that the air required for the ejector power may be suppliedeither from the engine bleed or from an auxiliary pump. It is also notedthat the velocity head at the engine inlet is used to provide the motivepower for movement of the contaminant particles and carrier air.

It is noted also that in the preferred form of the invention shown theparts are annular to conform to the engine inlet position andconfiguration, although important features of the invention could beaccomplished by rectangular or other shaped parts having substantiallythe same general cross-section as shown.

It can be seen that this invention presents advantages not heretoforeincorporated in separators for gas turbine engines. Less than 0.1% ofthe initial main air stream is lost in cleaning steps. Thus, thisinvention provides a separator which is of simple and economicalconstruction, is compact and provides for minimal maintenance.

While a present exemplary embodiment of this invention has beenillustrated and described it will be recognized that this invention maybe otherwise variously embodied and practiced by those skilled in theart.

What is claimed is:

1. A particle separator for removing particles from a stream of airsupplied to the inlet of a gas turbine engine, said separatorcomprising:

a first centrifugal separating station upstream of the inlet havinginner and outer curved walls wherein centrifugal force causes particlesand transport air to travel along the outer wall and the cleaned mainair stream passes to the inlet;

a second centrifugal separating station in series communication withsaid first station to receive the particles and transport air from saidouter wall, said second station forming a secondary air passage incommunication with the main air stream downstream of the first stationinlet and upstream of the inlet wherein clean air from said secondseparating station is inserted into the main air stream,

a third separating station in series communication with said secondseparating station for receiving particles and transport air from saidsecond separating station, said third separating station comprising aplurality of cyclonic tube separators for further separating particlesfrom the transport air, each cyclonic tube having a clean air outlet incommunication with a clean air chamber in flow communication with saidsecondary air passage wherein clean" air from said cyclonic tubes istransmitted to said secondary air passage and inserted into the main airstream, and a particle outlet in flow communication with a collectingchamber, and

ejector means in communication with said collecting chamber for ejectingparticles from said separator.

2. A particle separator for removing particles from a stream of airsupplied to the inlet of a gas turbine engine, said separatorcomprising:

a first centrifugal separating station comprising an annular radialinflow bellmouth upstream of the inlet having inner and outer curvedwalls wherein centrifugal force will cause particles in the stream ofair to travel along the outer wall;

a second centrifugal separating station in series with said firststation, said second station being formed by a curved deflector elementspaced from the terminating end of said outer wall, said deflectorelement forming a secondary air passage in communication with the mainair stream downstream of the first station inlet and upstream of theinlet, said deflector element being positioned to intercept and defleetparticles into said second separating station, said second separatingstation being in communication with said secondary air passage whereinclean air from the second separating station is inserted into the mainair stream;

a third separating station in series with said second separating stationfor receiving particles from said second station for final separation ofparticles from transport air, said third separating station having aclean air passage in flow communication with a clean air chamber, saidchamber being in communication with said secondary air passage whereinclean air therefrom is transmitted to said secondary air passage forinsertion into the main air stream, and a particle discharge passage inflow communication with a particle collecting chamber, and particleejector means in communication with said collecting chamber whereinparticles are transmitted to the exterior of the separator. 3. Aseparator as set forth in claim 2 in which said third separating stationcomprises a plurality of vortex 10 tube separators.

References Cited UNITED STATES PATENTS 3/1968 Connors 55-306 1/1969Beurer 55306 FRANK W. LU'ITER, Primary Examiner V. GIFFORD, AssistantExaminer

